Alkylation process



United States Patent Ofiice 2,883,440 Patented Apr. 21, 1959 ALKYLATION PROCESS John Raley, Walnut Creek, Califi, assignor to Shell Development Company, New York, N.Y., a corporation of Delaware N0 Drawing. Application May 21, 1957 Serial No. 660,480

14 Claims. (Cl. 260-671) lyzed processes for the alkylation of isoparafiins .with

olefins. Catalysts for these alkylation processes are mineral acids, such as sulfuric acid and hydrofluoric acid. Other acidic materials, e.g., aluminum chloride, may also serve as catalysts. In general, the systems utilizing; acidic catalysts are heterogeneous. They may also behomogeneous, e.g., when aluminum bromide is used in a liquid system.

It is also known to conduct the alkylation of parafiins with olefins thermally, at temperatures of 500 C. and higher and pressures of over 4000 p.s.i.g. Thermal alkylation is not today practiced commercially, although the reaction. may occur to some extent in so-called thermal polymerization processes in which, for example, mixed paraffinic and olefinic feeds of three to four carbon atoms per molecule are exposed to temperatures of 500-600 C. at pressures above 1000 p.s.i.g.

It has beenproposed to promote thev alkylation of parafiins with olefins by certain'so-called homogeneous catalysts to be usedin vapor phase. Specifically, organic halogen compounds andorganic nitro compounds have been proposed for use as suchcatalysts. These homogeneously catalyzed alkylation processes have not found commercial acceptance.- The homogeneous catalysts proposed heretofore have a variety of shortcomings. For example, many of the compounds are relatively expensive; many are quite corrosive; and many are diflicult to remove from thealkylation products. Generally, the catalysts can not be recovered and reused. This. makes most, if not all, the previously-proposed. compounds too expensive for commercial use.

The previously-proposed so-called homogeneous catalysts have the further disadvantage that, in alkylation of a paraffin. with an olefin, they lead-to the formation of a relatively high proportion of a saturated product.

which is not the product of reaction. between the originally charged paraffin and olefin, but is the productof reaction of molecules of the originally charged. olefin.

with other molecules thereof; ultimately saturated by a transfer of hydrogen atoms. In the production of gasoline, the saturated hydrocarbons produced by interreaction of the olefins aregenerally of much lower octane number than the true alkylation product.

It is an object of the present invention to. provide aneflicient' process for alkylating saturated hydrocarbons with olefinic hydrocarbons. Another object of this invention is to provide an efficient process for alkylating saturated aliphatic hydrocarbons with unsaturated aliphatic hydrocarbons to produce high yields of high octane gasoline. A. more specific object is to provide a process for alkylating isobutane:withethylene or propyl-- cue to produce high yields of high octane gasoline. Another object of this invention is to alkylate higher paraffinic hydrocarbons, e.g., waxes, with lower olefins, e.g., ethylene, to produce alkylation products having modified properties. Another object is to alkylate the alkyl portion of aryl-substituted alkanes (cyclic or noncyclic) with olefins. Other objects and advantages of the present invention will become apparent to those skilled in the art from the following description.

It has now been found that certain compounds not'recognized by the prior art for the purpose are especially suitable and advantageousnon-acidic promoters of alkyla-tion. These compounds are the organic disulfides. They are superior in tha they lead to the production of a liquid product containing arr-especially high ratio of the alkylate to the homo reaction product of the olefins. Further, some organic disulfides are readily and cheaply available-in theordinary petroleum refinery. They are relatively non-corrosive. The decomposition products of the disulfides may include mercaptans, which are readily removed from the resulting alkylate. If desired, mercaptans can be removed from the alkylate by a sweetening process in which they are converted back to disulfides which may then be'again used in the promotion of the alkylation.

Broadly stated, this-invention is a process for alkylatingsaturated.hydrocarbons, particularly paraifins, including aryl-substituted paralfins with olefinic hydrocarbons, which comprises contacting the saturated and the olefinichydroearbons in areaction zone under alkylating conditions with a small amount of an alkylation promoter. consisting essentially of an organic disulfide. Preferably the promoter forms with the hydrocarbon reactants a single homogeneous phase at the alkylation conditions of the reaction zone.

A number of advantages of the so-called homogeneous catalysis of alkylation have been described in the prior art. All of these advantages may be realized in the process of the present invention. Thus, the present invention permits the alkylation of normal as well as isoparaffinic hydrocarbons with olefins. Relatively low temperatures are employed compared to the non-catalytic thermal alkylation. Intimate contact is easily obtained in. homogeneous as contrasted to heterogeneous catalysis.

i of this invention and the acid-catalyzed alkylation processes is that the alkylation product itself is of a different chemical nature. For example, in the acid-catalyzed alkylation of isobutane with ethylene, which can be carried out over aluminum chloridecatalyst, the predominant alkylation product is 2,3-dimethylbutane, also known as diisopropyl. By contrast, the alkylation of isobutane with ethylene according to the present invention leads to the formation of 2,2-dimethylbutane, also known as neohexane, to the substantial exclusion of diisopropyl. When reading isobutane with propylene by means of acidic alkylation catalysts, the predominant alkylation products are 2,3-dimethylpentane and 2,4-dimethylpentane. In the alkylation of isobutane with propylene in accordance with this invention, the predominant alkylation product is 2,2- dimethylpentane.

In general, the product of alkylation in this process is the result of the least substituted carbon of the double bond being joined directly to a tertiary carbon atom of an isoparaffin or to a secondary carbon atom of a normal paraflin. The resulting products are recovered as such from the reaction.

In the broadest aspect, the alkylation promoters of this invention are organic disulfides, i.e. compounds having the formula R-S-S-R' wherein R and R may be identical or they may be two different groups of the same type or they may be groups of diflerent types. Ordinarily the simplest organic disulfides are preferred because they serve the purpose adequately and are more readily and cheaply available than more complex compounds. For example, dimethyldisulfide and diphenyldisulfide have been successfully used in the process of this invention and are preferred alkylation promoters. Other suitable disulfides are, for example, the dialkyldisulfides in which the groups R and R' are methyl, ethyl, propyl, isopropyl, n-butyl, sec. butyl, tert. butyl, and the various forms of amyl, hexyl and similar alkyl groups. Other suitable disulfides are the diaryldisulfides in which R and R are phenyl, tolyl, xylyl or other polymethylphenyl groups or other phenyl groups having from one to five alkyl substituents of from one to four carbon atoms, each. Other suitable disulfides are dicycloalkyldisulfides, e.g., those in which R and R are cyclopentyl, cyclohexyl and alkyl-substituted cyclopentyl or cyclohexyl groups, such as those having from one to five substituents of from one to four carbon atoms, each. The disulfide may also be methylphenyldisulfide or another alkylaryldisulfide or an alkylcycloalkyldisulfide or a cycloalkylaryldisulfide. All of the above-named compounds are dihydrocarbyldisulfides, i.e. compounds in which both R and R represent a monovalent hydrocarbon radical.

Although the dihydrocarbyldisulfides are preferably used in the process of this invention, other organic disulfides may also be suitably employed, e.g., diacyldisulfides and diaroyldisulfides, substituted phenyldisulfides such as p,p-dianisyldisulfide, substituted dialkyldisulfides such as dithioglycolic acid, and others.

The disulfides employed as promoters need not be pure compounds but may be mixtures of disulfides, e.g., the mixture which is produced in the sweetening of sour hydrocarbon fractions in which mercaptans are converted to disulfides. The disulfides resulting in such sweetening processes are predominantly mixed dihydrocarbyldisulfides having boiling points slightly higher than the hydrocarbon fraction being treated. Disulfides suitable for this invention are, for example, produced in the sweetening of liquefied petroleum gases, gasoline or kerosene.

The alkylation promoters of this invention may be solids, liquids or gases under normal conditions. Preferred disulfides for use in the process of this invention are those having from two to twenty carbon atoms per molecule and'having such volatility or solubility that they exist in the same phase as the reactants under alkylation conditions.

The amount of organic disulfides used varies from about 0.1 to about 5 mole percent based on the total hydrocarbon charge. It is preferably between about 0.4 and about 1.4 mole percent. For a given system of hy drocarbon reactants and alkylation conditions there is generally an optimum range of the amount of promoter to be employed which leads to best results. Use of insufficient or excessive amounts of promoter tends to favor the production of undesired reaction products of the olefins at the expense of the desired alkylate.

The saturated, i.e. non-olefinic, hydrocarbon component of the reaction mixture may be any saturated hydrocarbon having three or more carbon atoms per molecule. Normal and branched parafiins are particularly suitable. Fully or partially hydrogenated non-olefinic cyclic hydrocarbons may also be alkylated in accordance with this process. This includes cyclopentane, cyclohexane, their alkyl derivatives, decalin, tetralin and others.

The olefinic reactant maybe any olefinic hydrocarbon having two or more carbon atoms per molecule. Nonconjugated olefins, and particularly mono-olefins are preferred. Ethylene and propylene are particularly suitable and are especially preferred in many cases, but higher olefins, e.g., butene-l, butene-2, isobutene, the normal andbranched pentenes, hexenes, heptenes, octenes and higher olefins may also be employed as alkylating agents.

When the alkylation process is carried out for the purpose of producing gasoline, the preferred saturated reactant is isobutane and the most preferred olefin reactant is propylene. Ethyleneor mixed butenes are also very suitable olefin feed stocks in the alkylation of isobutane. Other suitable parafiinic feed stocks for the production of motor gasoline are propane, n-butane and the pentanes, particularly isopentane. n-Hexane and methylpentanes are also suitable, especially when the olefin is ethylene or propylene.

Long-chain parafiins having from about fifteen to about thirty carbon atoms per molecule are very suitable feed components for a liquid phase alkylation, particularly with ethylene.

Aryl-substituted alkane hydrocarbons suitable for alkylation include toluene, the polymethylbenzenes, ethylbenzene, polyethylbenzenes, other alkylbenzenes and polyalkylbenzenes, e.g., cumene and polyisopropylbenzenes, alkyland polyalkylnaphthalenes, and so forth.

The temperatures used in the alkylation reaction zone of this invention are in the range from 200 to 550 C., inclusive. The preferred temperatures are in the range of from 300 to 450 C. At the higher temperatures in the given range, the higher pressures in the range specified below are necessary.

Reaction times are generally in the range of from onehalf hour to twenty hours. Longer reaction times are not required. Shorter ones may be employed, down to five to ten minutes. The shorter times are useful at the higher temperatures in the ranges given.

The pressures used in the alkylation are in the range of from about 650 p.s.i.g. to about 15,000 p.s.i.g. or more, preferably from about 750 p.s.i.g. to about 2,500 p.s.i.g.

As in other alkylation processes, the selectivity to the desired alkylation product is increased by maintaining a relatively high ratio of saturated compound to olefin in the alkylation reaction zone. The molar ratio of saturated hydrocarbon to olefinic hydrocarbon should be at least about 1:1 and is preferably in the range of from 2:1 to 10:1. Higher ratios may be employed.

The process of the invention may be carried out in batch or in continuous reaction systems. In a batch system the reaction mixture of saturated and olefinic hydrocarbon and organic disulfide is charged to a reaction vessel, e.g., an autoclave, where it is rapidly heated to reaction conditions of temperature and pressure. It is also convenient to inject additional olefin, and sometimes, additional disulfide into the mixture during the course of the reaction.

In-a continuous reaction system, a mixture of saturated and olefinic hydrocarbon and organic disulfide is passed through a reaction zone which may be, for example, a series of chrome-steel or chrome-nickel steel tubes in a furnace, maintained at the desired reaction temperature and pressure. There may be a soaking zone, such as a drum, following the tubular heater.

When the reaction is completed, either in a batch or continuous system, the reaction mixture is treated to recover the desired product. For example, in the production of gasoline by alkylation of hydrocarbons having three and four carbon atoms per molecule, the reaction product is fractionated to stabilize it by removing the normally gaseous hydrocarbons, which may be returned to the reaction zone. A liquid alkylate fraction of the desired boiling range is recovered as a gasoline product.

In the production of gasolinehydrocarbons; the di-' sulfide may be chosen such that its decomposition products are'not found. in the gasoline boiling: range. For example, when dimethyldisulfide is employed, the decomposition products include methyl mercaptan which is withdrawn with the gaseous portion of the reactor eflluent. In such a case the liquid alkylation product needs no further sweetening treatment to be suitable for use as a gasoline. Where portions of the mercaptan resulting from decomposition of the disulfide promoter are present in the gasoline reaction product, the latter may be subjected to a conventional sweetening operation,- such as Doctor sweetening, solutizer sweetening, hypochlorite sweetening or other known methods. If an extractive method is employed coupled with solvent'regeneration, the'disulfides recovered from the sweetening process are suitably separated and used as promoter in the-alkylation reaction.

The following examples are illustrative of the present invention but are not to be considered limitingv thereon.

EXAMPLE I Run No. l, a typical run in accordance with the present invention, was made in the following manner: A. sealed frangible vial containing a weighed amount of diphenyldisulfide was placed in a stainless steel rocking autoclave, which was then closed, evacuated and weighed. Isobutane was then admitted by direct connection to a tank while the vessel was chilled in ice. The vessel was allowed to warm to room temperature and was again accurately weighed. Ethylene was then admitted by direct connection to a cylinder; after ethylene addition was completed the vessel was again weighed. The vial of diphenyldisulfide was then broken and the autoclave was rapidly heated to a temperature of 40.0" C., at which temperature it was maintained for a period of one hour. The pressure in the vessel at reaction conditions was approximately 1000 p.s.i.g. In this run, the mole ratio of isobutane to ethylene was 24:1 and the amount of 'diphenyldisulfide expressed as mole percent based on the total hydrocarbons, was 0.5%.

After completion of the reaction the vessel was cooled to room temperature, weighed to insure absence of loss due to leakage, and evacuated by connecting it through a series of cold traps to a gas holder. Complete removal of product from the autoclave was insured by heating the vessel to 120-130 C. at 1 mm. pressure. The recovered liquid and gas were analyzed chromatographically. After removal of all product the autoclave was again weighed and the increase in weight reported as residue.

The. product distribution observed in Run No. 1 is reported in Table I. In this run 98% by Weight of the charge was accounted for in the recovered material. Conversion of ethylene was 53.2%; conversion of is-o Table 1. I PRODUCT DISTRIBUTION IN RUN NO. 1

Product Product Selectivity, Percent by Composi- Moles per Wt. based tion, 100 Moles on total Percent Carbon O1H4 Hydroby Wt. Number Compound Reacted carbons based on Charged 0t Product 0.6 0. 03 0.2 3. 9 0. 5 2. 4 0.6 0.1. 0. 4 '4. 8 0. 9 4. 4 1. 9 0. 4 2.1 2,2-Dhnethylbutan 47. 6 l3. 2 66. 4 2,3-Dimethylbutane 0 0 0 2,2Dimethylhexane 4. 6 1. 7 8. 6 2-Methylpentane 2. 5 0. 7 3. 5 Unidentified C3 and 2. 7 13. 8

Heavier.

"Most of reported 04 was in original feed.

The data in the last. column of Table I shows that 66.4% by weight'of the total product was 2,2-dimethylbutane and that no 2,3-d-imethylbutane was produced. The recovered ethane is a reaction product of the feed ethylene. The materialof four carbon atoms per molecule is mainly n-butane, which was present as an impurity in the feed. The only substantial amount of identified liquid product other than 2,2-dimethylbutane is 2,2- dirnethylhexane, which occurred as about 8% by weight of the totalproduct; an unidentified liquid product occurred in about 14% concentration. The latter appears to be predominantly or entirely the product of the polymerization of ethylene, saturated by a subsequent hydrogen exchange.

EXAMPLE 11 Run No. 2 was carried out in a similar manner to Run No. 1 but using, instead of organic disulfide, nitromethane, a homogeneous catalyst of the prior art. The run was carried out at 370 C. with a reaction time of one hour. The isobutane-to-ethylene mole ratio was 2.5:1. Theconversion'of ethylene was 53.9% while that of isobutane was 5.8%. The selectivity (moles product per 100 moles C H charged) to 2,2-dimethylbutane Was only 6.5% in this run; that to 2,2-dimethylhexane Was 1.6%. The amount of unidentified C and heavier organic product was 4.9% by weight, based on total hydrocarbons charged. No significant amount of 2,3-dimethylbutanewas found.

EXAMPLE III Runs Nos. 3 through 14 were carried out in a similar manner to Run No. 1 described in Example I, but with varying conditions of time and temperature and with some variation in organic disulfide. and feed olefin. The conditions under which these runs were carried out and the conversion of olefin and selectivity to 2,2-dimethylbutane was 13.9% butane (in runs using ethylene) are given in Table II.

Table II I Run Number 3 4 5 6 7 8' 9 10 11 12 13 14 Feed Hydrocarbons:

Paraifin Isobu- 'Isobu- Isobu- Isobu- Isobu- Isobu- Isobu- Isobu- Isobu- Isobu- Isobu- Isobutane tane tane tane tane tane tane tane tane tane tane tane Olefin Eth- Etlzh- Etlzhgh- Etlzh- Etlzh- Etlm- Etih- Eti'h- Etih- Eth- Proy ene y we y ene y ene y ene y ene y ene y en ene ene lene lene Mole Ratio: Paraffin-Olefin 2.2 2.1 2. 5 2. 1 2. 2 2,3 2.0 2.3 y 2.4 y 2.3 y 1. 2 Dy 1. 8

Promoter .L OHa-S-S-CHa GHE- 'S-CaHE OH3S-SCH3 Concentration, Mole Percent .1- 1. 1 1. 1 1. 3 1. 2 1. 0 1. 3 1. 1 1. 1 0. 5 1. 1 1.0 1. 1 Conditions:

Time, Hrs 17 8. 4 2. 5 0. 6 0. 5. 12 12 1 0.5 17 17 Temp, O 350 350 350 400 400 425 300 350 400 400 350 360 Pressure. p.s.1.g ea. ca. ea. ca. ca. ea. ca. ca. ca. ca. ea. ca.

, p 1, 000 1, 000 1, 000 1, 000 1, 000 1,000 1, 000 1, 000 1, 000 1, 000 1, 000 1, 000 Conversion: Percent of Olefin Converted 49 36 83 58 24 48 5 53 Selectivity, Mole Percent:

2,2-Dimethylbutane 2,2-Dimethylhexane I 2,2-Dimethylpentnne I 1 Methylcyclopentane 3. 'Other- Grand-C Hydrocarbons 7 7 Runs Nos. 3 through 5 illustrate the effect of decreasing reaction time from seventeen to four hours at 350 C. and Runs Nos. 6 and 7 the efiect of decreasing the time from 2.5 to 0.5 hours at 400 C. Runs Nos. 7 and 8 permit comparison of results obtained at otherwise sim-' ilar conditions at 400 and 425 C., respectively. Runs Nos. 3-18, 13 and 14 were carried out with dimethyldisulfide promoter. Runs Nos. 9 through 12 were carried out with diphenyldisulfide promoter. In Runs Nos. 9 through 12 the temperature was increased from 300 to 400 C. and the contact time decreased from twelve to 0.5 hours. Run No. 13, when compared to Run No. 3, illustrates the loss in selectivity on decreasing the isobutane-to-ethylene mole ratio from 2.2:1 to 12:1.

EXAMPLE IV Run No. 15 was carried out in a similar manner to Run No. 1 but using toluene instead of isobutane as the saturated feed component. The run was carried out at 400 C. with a reaction time of two hours. The tolueneto-ethylene mole ratio was 2.5 :1. The conversion of ethylene was 65.8% while that of toluene was 16.4%.

The major reaction product observed was n-propylbenzene. The selectivity of formation of this compound was 43.4 moles per 100 moles of ethylene consumed.

EXAMPLE V When isobutane is alkylated with propylene in a manner similar to that described in Example I, but employing a temperature of 225 C., the pressure which must be employed to obtain at least 75% conversion of propylene is at least about 8 p.s.i.a. At such a low pressure and temperature, however, the reaction rate is much too low to be useful and a pressure of at least 650 p.s.i.g. is, therefore, employed. The minimum pressure required for 75 conversion at 325 C. is about 300 p.s.i.g.; here again, at least 650 p.s.i.g. is employed to bring up the rate. At 425 C. the minimum pressure is 4,200 p.s.i.g. and at 525 C. it is 26,500 p.s.i.g.

When isobutane is alkylated with ethylene at similar conditions, the minimum pressure is lower, in each case, than that required with propylene. When the olefin is butylene or higher, the corresponding minimum pressures are somewhat higher.

When propane is used instead of isobutane, the minimum pressures are, again, somewhat lower than corresponding pressures for isobutane. Similarly, when the saturated compound is heavier than isobutane the minimum pressure is somewhat higher in each case.

I claim as my invention:

1. A process for alkylating a first hydrocarbon of the group consisting of saturated hydrocarbons and aryl substituted alkanes with an olefinic hydrocarbon which comprises exposing a reaction mixture containing at least about one mole of first hydrocarbon per mole of olefinic hydrocarbon and containing from 0.1 to 5 mole percent, based on total hydrocarbons, of a dihydrocarbyl disulfide as the sole alkylation catalyst present to a reaction temperature of at least about 200 C. and below that at which substantial thermal cracking of said hydrocarbons takes place at a pressure of at least about 650 p.s.i.g., higher pressures being employed at higher temperatures in the stated range.

2. A process in accordance with claim 1 in which said first hydrocarbon is a paraflin.

3. A process in accordance with claim 1 in which said first hydrocarbon is an aryl-substituted parafiin.

4. A process in accordance with claim 1 in which said disulfide is a dialkyl disulfide wherein each alkyl radical contains 1-6 carbon atoms.

5. A process according to claim 1 in which said di sulfide is dimethyldisulfide.

6. A process in accordance with claim 1 in which said a range hydrocarbons which comprises exposing a reaction mixture containing a paraflinic hydrocarbon having from three to six carbon atoms per molecule and an olefinic hydrocarbon having from two to five carbon atoms per molecule, in a ratio of at least about one mole of paraflin per mole of olefin and containing from 0.1 to 5 mole percent, based on total hydrocarbons, of a dihydrocarbyl disulfide as the sole alkylation catalyst present in vapor phase to a reaction temperature of at least about 200 C. and below that at which substantial thermal cracking of said hydrocarbons takes place at a pressure of at least about650 p.s.i.g., higher pressures being employed at higher temperatures in the stated range.

8. A process in accordance with claim 7 in which the disulfide is a diaryldisulfide wherein at least one of the aryl radicals bear 05 alkyl substituents of l-4 carbon atoms each and the paraflin is an isoparaffin.

9. A process for the production of gasoline boiling range hydrocarbons which comprises exposing a reaction mixture containing isobutane and an olefin having from two to three carbon atoms per molecule in a ratio of at least two moles of isobutane per mole of olefin and containing from 0.1 to 5 mole percent of a dihydrocarbyldisulfide in which the hydrocarbyl radicals are selected from the group consisting of methyl and phenyl radicals in vapor phase to a reaction temperature in the range between 300 and 450 C. at a pressure in the range between about 750 and about 2,500 p.s.i.g., the higher pressures being employed at the higher temperatures in the stated range.

10. A process in accordance with claim 9 in which said olefin is ethylene and in which the reaction product contains a substantial proportion of neohexane.

11. A process in accordance with claim 9 in which said olefin is propylene and in which the reaction product contains a substantial proportion of neoheptane.

12. A process for the production of a branched-chain hydrocarbon in the lubricating oil boiling range which comprises exposing a reaction mixture containing a longchain paraffin having from fifteen to thirty carbon atoms per molecule and an olefinic hydrocarbon, in a ratio of at least two moles of paraflin per mole of olefin, and containing from 0.1 to 5 mole percent, based on total hydrocarbons, of a dihydrocarbyl disulfide as the sole alkylation catalyst present in liquid phase to a reaction temperature of at least about 200 C. and below that at which substantial thermal cracking of said hydrocarbons takes place at a pressure of at least about 650 p.s.i.g., higher pressures being employed at higher temperatures in the stated range.

13. A process for the alkylation of an aryl-substituted alkane hydrocarbon which comprises exposing a mixture containing an aryl-substituted alkane and an olefinic hydrocarbon, at a ratio of at least one mole of arylalkane per mole of olefin and containing from 0.1 to 5 mole percent, based on total hydrocarbons, of a dihydrocarbyl disulfide as the sole alkylation catalyst present to a reaction temperature of at least about 200 C. and below that at which substantial thermal cracking of said hydrocarbons takes place at a pressure of at least about 650 p.s.i.g., higher pressures being employed at higher temperatures in the stated range, and recovering from the reaction mixture an alkylated aryl-substituted alkane hydrocarbon in which the aryl group has no more nuclear alkyl group substituents than the aryl group in the feed arylalkane hydrocarbon.

14. A process according to claim 1 wherein the olefin contains 2-8 carbon atoms per molecule.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A PROCESS FOR ALKYLATING A FIRST HYDROCARBON OF THE GROUP CONSISTING OF SATURATED HYDROCARBONS AND ARYL SUBSTITUTED ALKANES WITH AN OLEFINIC HYDROCARBON WHICH COMPRISES EXPOSING A REACTION MIXTURE CONTAINING AT LEAST ABOUT ONE MOLE OF FIRST HYDROCARBON PER MOLE OF OLEFINIC HYDROCARBON AND CONTAINING FROM 091 TO 5 MOLE PERCENT, BASED ON TOTAL HYDROCARBONS OF A DIHYDROCARBYL DISULFIDE AS THE SOLE ALKYATION CATALYST PRESENT TO A REACTION TEMPERATURE OF AT LEAST ABOUT 200* C. AND BELOW THAT AT WHICH SUBSTANTIAL THERMAL CRACKING OF SAID HYDROCARBONS TAKES PLACE AT A PRESSURE OF AT LEAST ABOUT 650 P.S.I.G., HIGHER PRESSURES BEING EMPLOYED AT HIGHER TEMPERATURES IN THE STATED RANGE. 